Remove unused methods

[ Merge of http://go/wvgerrit/16405/ ]

Methods in string conversion and license request tests were not being used.
This was detected by static analysis cppcheck reports.

b/26349052

Change-Id: I44779abf6b6fdc01b5391bff7d47be1d20ef84d2

libwvdrmengine/cdm/core/include/string_conversions.h

@@ -20,7 +20,6 @@ std::string Base64SafeEncodeNoPad(const std::vector<uint8_t>& bin_input);
 std::vector<uint8_t> Base64SafeDecode(const std::string& bin_input);
 std::string HexEncode(const uint8_t* bytes, unsigned size);
 std::string IntToString(int value);
-std::string UintToString(unsigned int value);
 int64_t htonll64(int64_t x);
 inline int64_t ntohll64(int64_t x) { return htonll64(x); }